The present invention generally relates to network signaling.
The known signaling architecture H.323 is an International Telecommunications Union (ITU) defined standard that describes how multimedia communications occur between terminals, network equipment and services on local area networks (LANs) and wide area networks (WANs) that do not provide a guaranteed quality of service (such as Internet Protocol (IP) networks). Quality of service is a measure of communication service quality during a call, and can include, for example, the bandwidth, delay and latency associated with the call. In networks using connectionless “best effort” delivery models, the quality of service typically is not guaranteed; the H.323 is a signaling architecture for such a network.
The H.323 provides a range of implementation options including gatekeeper-routed signaling. In the H.323 standard, gatekeepers map LAN address aliases to IP addresses and provide address lookups when needed. Gatekeepers also exercise call-control functions to limit the number of H.323 connections and the total bandwidth used by these connections in an H.323 “zone.” Although the gatekeeper is not necessary within the H.323 standard, when a gatekeeper is present in a network, network terminals must make use of its services. In other words, gatekeepers maintain state information for each individual call and all call signaling must pass through the gatekeepers.
The gatekeeper implementation of the H.323 standard, however, suffers several shortcomings. First, the equipment associated with gatekeepers needs to be extremely reliable so that the gatekeeper is available throughout the course of the call. If the gatekeeper-related equipment fails during a call, the call fails because the state information for the call maintained solely at the gatekeeper is lost. Second, the gatekeeper-related equipment likely cannot scale in a cost effective manner because maintaining the state information and performing the messaging associated with H.323 is complex and processor intensive. Finally, theft of service is possible by bypassing the gatekeepers to place unauthorized and unmonitored calls.